Meditation, deep breathing and yoga comprise nearly a quarter of all CAM usage, although little is known about the neurobiological mechanisms by which meditative techniques exert their effects on health. Many of the disorders for which meditation is used, such as chronic pain, anxiety and drug addiction, are characterized by abnormal emotional experiences, abnormal perceptions of body states, and abnormal activity in brain networks that give rise to awareness of the internal state of the body. The practice of meditation explicitly highlights the importance of awareness directed towards the body, across tradition and experience level. The effectiveness of meditative techniques as a treatment for these disorders may lie in their ability to change awareness of the internal state of the body, by modifying the function of this brain network. The purpose of this project is to examine how meditation changes interoception: awareness of the internal state of the body. Rather than examining neural activity during the meditative state, I propose to examine neural activity during performance of an interoceptive task: heart beat detection. This task draws on components of the meditative process but is better characterized, providing quantifiable information about the nature of the subject's experience. Two studies will be conducted. The first will compare brain activity during heartbeat detection between experienced and beginning meditators. The second will longitudinally track changes in brain activity during heartbeat detection that result from learning the practice of meditation.